Promoting effect of H2O over macroporous Ce-Zr catalysts in soot oxidation

•Soot oxidation activities of ceria-based catalysts were enhanced in the presence of H2O.•In the presence of H2O, −OH groups as well as oxygen vacancies on the catalytic surface increased.•Isotope experiments and DFT calculations show that the generation of active oxygen from H2O was preferred to that from O2•When the morphology was retained during thermal aging, the catalytic performance under wet condition was maintained.